Search Results

Large diameter, tightly toleranced fastener patterns are commonplace in aerospace structures. Satisfactory generation of these holes is often challenging and can be further complicated by difficult or obstructed access. Bespoke tooling and drill jigs are typically used in conjunction with power feed units leading to a manual, inflexible, and expensive manufacturing process. For 777X flap production, Boeing and Electroimpact collaborated to create a novel, automated solution to generate the fastener holes for the main carrier fitting attachment pattern. Existing robotic automation used for skin to substructure assembly was modified to utilize extended length (up to 635mm), bearing-supported drill bar sub-assemblies. These Long Assembly Drills (LADs) had to be easily attached and detached by one operator, interface with the existing spindle(s), supply cutting lubricant, extract swarf on demand, and include a means for automatically locating datum features.

Low rate initial production of the 777X flight control surfaces and wing edges has been underway at the Boeing St. Louis site since early 2017. Drilling, inspection, and temporary fastening tasks are performed by automated multi-function robotic systems supplied by Electroimpact. On the heels of the successful implementation of the initial four (4) systems, Phases II and III are underway to meet increasing production demands with three (3) and four (4) new cells coming online, respectively. Assemblies are dedicated to particular cells for higher-rate production, while all systems are designed for commonality offering strategic backup capability. Safe operation and equipment density are optimized through the use of electronic safeguards. New time-saving process capabilities allow for one-up drilling, hole inspection, fastening, fastener inspection, and stem shaving.

Fabrication and assembly of the majority of control surfaces for Boeing’s 777X airplane is completed at the Boeing Defense, Space and Security (BDS) site in St. Louis, Missouri. The former 777 airplane has been revamped to compete with affordability goals and contentious markets requiring cost-effective production technologies with high maturity and reliability. With tens of thousands of fasteners per shipset, the tasks of drilling, countersinking, hole inspection, and temporary fastener installation are automated. Additionally and wherever possible, blueprint fasteners are automatically installed. Initial production is supported by four (4) Electroimpact robotic systems embedded into a pulse-line production system requiring strategic processing and safeguarding solutions to manage several key layout, build and product flow constraints.

A robotic arm manipulator is often an appealing method to position drills, bolt inserters, automated fiber placement heads, or other end effectors. In a standard robot the flexibility of the cantilevered arm as well as backlash in the drive system lead to large positioning errors. Previous work has greatly reduced this error through the use of secondary scales and a mathematical model of the robot deflection running on a CNC controller. Further research improved upon this model by accounting for linear deformation of each robot link regardless of position. The parameters describing these deformations are determined through a calibration routine and then used in real time to guide the end effector accurately to any reachable pose. In practice this method has been used to achieve total on-part positioning accuracy of better than +/− 0.25mm.

The processes of drilling and milling Boeing 737 inboard flaps at Triumph Aerostructures have been enhanced by an accurate articulated robotic system. Tool point positioning is handled by an off-the-shelf 6-axis KUKA KR360 robot riding on a linear axis. Each of the 7 axes is enhanced with secondary position encoders. A single process head performs all required functions, including one-sided pressure application, touch probing, barcode scanning, drilling/countersinking, measurement of hole diameter and countersink depth, and face milling. The system is controlled by a Siemens 840Dsl CNC which handles all process functions, robot motion, and executes software technologies developed for superior positional accuracy including enhanced kinematics, automated normality correction, and anti-skid correction. The layout of the assembly cell allows the robot to span four fixture zones.

Serial link articulated robots applied in aerospace assembly have largely been limited in scope by deficiencies in positional accuracy. The majority of aerospace applications require tolerances of +/−0.25mm or less which have historically been far beyond reach of the conventional off-the-shelf robot. The recent development of the accurate robot technology represents a paradigm shift for the use of articulated robotics in airframe assembly. With the addition of secondary feedback, high-order kinematic model, and a fully integrated conventional CNC control, robotic technology can now compete on a performance level with customized high precision motion platforms. As a result, the articulated arm can be applied to a much broader range of assembly applications that were once limited to custom machines, including one-up assembly, two-sided drilling and fastening, material removal, and automated fiber placement.

Once limited by insufficient accuracy, the off-the-shelf industrial robot has been enhanced via the integration of secondary encoders at the output of each of its axes. This in turn with a solid mechanical platform and enhanced kinematic model enable on-part accuracies of less than +/−0.25mm. Continued development of this enabling technology has been demonstrated on representative surfaces of an aircraft fuselage. Positional accuracy and process capability was validated in multiple orientations both in upper surface (spindle down) and lower surface (spindle up) configurations. A second opposing accurate robotic drilling system and full-scale fuselage mockup were integrated to simulate doubled throughput and to demonstrate the feasibility of maintaining high on-part accuracy with a dual spindle cell.

The effectiveness of serial link articulated robots in aerospace drilling and fastening is largely limited by positional accuracy. Unguided production robotic systems are practically limited to +/-0.5mm, whereas the majority of aerospace applications call for tolerances in the +/-0.25mm range. The precision with which holes are placed on an aircraft structure is affected by two main criteria; the volumetric accuracy of the positioner, and how the system is affected when an external load is applied. Production use and testing of off-the-shelf robots has highlighted the major contributor to reduced stiffness and accuracy as being error ahead of the joint position feedback such as backlash and belt stretch. These factors affect the omni-directional repeatability, thus limiting accuracy, and also contribute to deflection of the tool point when process forces are applied.

The second generation of Electroimpact's ONCE robotic drilling system has been successfully deployed in production. The automated system for drilling and inspection of skins to substructure in trailing edge flaps comprises an off-the-shelf KUKA KR360 robot integrated with an Electroimpact process head, 7th axis linear rail, and roll-over assembly fixture. The process includes drilling up to 3/8″ in diameter holes, countersinking, and inspection of CFRP/AI/Ti stacks using a 20k rpm, ATC spindle. Automated vision feature recognition and auto-normalization capabilities ensure proper hole vector and location with verification of diameter, countersink depth, stack thickness, and drill thrust being measured in-process. Tailored nose pieces enable access to nearly 100% of the structure with flood coolant, compliant tip, and vacuum swarf extraction capability.

Demand in Aerospace for assembly systems utilizing industrial robots is rapidly increasing. Robotic systems can often be implemented for smaller, labor intensive products where work is performed from a single side (e.g. close out of skins to spars/ribs). To justify the costs of automation and to maximize build efficiency, the industry is striving toward “one-up” assembly, whereby the product is assembled one time - drilled, inspected, and ultimately fastened - without removal of components for deburring, cleaning, sealing, etc. To qualify this for production on The Boeing Company’s 787 moveable trailing edge (MTE) assemblies, the robotic systems required certain key capabilities to not only produce a quality process, but also verify quality via highly developed measurement systems.

Automated Fiber Placement (AFP) equipment has been developed capable of laying fiber in excess of 2000 inches per minute on full-size, complex parts. Two such high-speed machines will be installed for production of a nose section for a large twin-aisle commercial aircraft fuselage at Spirit AeroSystems in Wichita, Kansas along with a rotator for the fuselage mandrel. The problem of cutting and adding on the fly at these speeds requires thorough re-evaluation of all aspects of the technology, including the mechanical, controls, servos systems, and programming systems. Factors to be considered for high speed cut and add on the fly are discussed.

The ONCE robotic drilling system utilizes a mass produced, high capacity industrial robot as the motion platform for an automated drilling, countersinking, and hole inspection machine for the skin to substructure join on the F/A-18E/F Super Hornet wing trailing edge flaps (TEF). Historically, robots have lacked the accuracy, payload capacity, and stiffness required for aerospace drilling applications. Recent improvements in positional accuracy and payload capacity, along with position and stiffness compensation, have enabled the robot to become an effective motion platform. Coupled with a servo-controlled multifunction end effector (MFEE), hole locations have successfully been placed within the specification's +/-0.060″ tolerance. The hole diameters and countersinks have proven to be very accurate, with countersink depth variation at 0.0025″ worst case.

Electroimpact developed an end effector for Airbus UK, Ltd. for use on a Kuka KR350 robot provided by Airbus UK. The end effector is referred to as the DDEE (Drill and Drive End Effector), and incorporates four main functions. The end effector pushes up on a wing panel with programmable pressure, drills a hole with a servo-servo drill, inspects the hole with a servo ball-type hole gauge and then drives a pin-tail style lockbolt into the hole. The end effector is being used as part of a development and feasibility study for incorporating automation into the wing panel manufacture process.

Early versions of handheld (HH) electromagnetic riveters (EMR), while effective, were heavy. With the proven effectiveness of the EMR, the next step was to make the HH riveting system light and portable. To maintain the required output force in a small package, the upper limit of the voltage range was increased to 1000V, twice that of conventional 500V LVER systems. The 0-1000V range of the HH50s allows for the formation of rivets up to 3/16″ diameter. Due to the lower mass in the HH50s, the riveting actuator was developed to strategically maximize output force and minimize recoil. Recent developments have been made to drastically reduce recoil by incorporating a spring-damper system integral to the HH50 handle.